Engineering Survey in the Construction Industry ď‚– Kenyan Case Presented By Erick Rapela & Noah Kertich
Introduction A Survey Engineer is very instrumental in the view that he is the only individual that is necessary at project inception(design) as well as completion (as built). In Kenya, he is considered a field person thus if not careful may be locked out of the critical decisions concerning the project. Must be a dynamic individual. Other countries like Australia a building surveyor will be consulted on issues relating to cost, design, insurance etc. A surveyor is involved at both the design stage and construction (implementation) stage of a project.
Responsibilities Investigating land, using computer-based measuring instruments and geographical knowledge, to work out the best position to construct bridges, tunnels and roads; Producing up-to-date plans which form the basis for the design of a project; Setting out a site, so that a structure is built in the correct spot and to the correct size; Monitoring the construction process to make sure that the structure remains in the right position, and recording the final asbuilt position; Providing control points by which the future movement of structures such as dams or bridges can be monitored.
Components of Survey Eng
Topographical Surveys Existing infrastructure/structures Underground – invert levels e.g. sewer, drainage Utility Survey- KPLC, water, communication(fiber optic) Setting out/ Lay out Control Cadastral – establish land boundaries
Surveyors’ Tools
GPS (Geodetic and Handheld) Total Stations Levels (spirit level, dumpy level, digital level, and laser level) Optical square ‘Hammer & peg’ Cable detector (transmitter and locator) Software – AutoCAD, CivilCAD, ArcGIS etc Internet – GoogleMaps, GoogleEarth etc Common terms in use: Chainage, offset, profile, alignment, cross-section, volumes, ogl
Control Survey Used to establish highly accurate positions (horizontal control) and elevations (vertical control) of select points or stations For control at least one station of known coordinates must be known (SOK points) Monumentation – stable points We can use a Total station traverse or Static GPS survey (geodetic network) Accurate/precise leveling
Topographical survey May be concerned with local detail in general, including not only relief but also vegetative and artificial features, and even local history and culture AS-IS survey Terrain – contours, profile Description – place names
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Earthworks Involves Cut (excavation)/Fill (embankment) quantities Excavation- the amount of material that needs to be removed from the grade. Embankment- the amount of material that needs to be added to the grade. Excavation and embankment are calculated with cross sections using the average end area method. Volume computation – compare two surfaces e.g. proposed vs existing
Sample Cross-section ï‚–
Mass Diagram Mass haul is a factor of volume of material and the distance moved during construction along an alignment. We have free (balance) and over haul volumes To construct a MHD (you require an alignment, two surfaces and material list). Mass diagrams determine the average haul, free haul, and overhaul on a given segment of roadway. Mass diagrams tell the contractors and inspectors the quantity of material moved and how far it can be economically moved (limits are at times set)